guru meditation running memtest in guest

I was running memtest inside a guest that had just been running Ubuntu 9.10. I've done this before without problems.
(I know that isn't a good way to test memory; I was using it as a quick and dirty wipe of the guest's memory.)

A message popped up saying there was a critical error, telling me to send in a bug report, and advising that I shut down the VM, but giving me the option of leaving it running for debugging. (Sorry, no such skills here.)

i am able to consistantly reproduce this bug. I am running host AMD64 based debian
uanme -a
Linux allamonkey 3.2.0-3-amd64 #1 SMP Mon Jul 23 02:45:17 UTC 2012 x86_64 GNU/Linux
virtualbox 4.1.18_debian r78361
I am attempting to install Ubuntu quantal with the 20101020ubuntu186 installer, both 32 and 64-bit versions.
Host hardware passes 48 hour memtest endurance burnin with zero errors
after install of quantal ubuntu, installer reboots and goes into memtest (no grub), which fails after a few minutes. Will attach log shortly. This is obviously two bugs... the preseeding file I am using somehow is failing to install any kernel other than the memtest, so it boots to memtest. But memtest should not fail, which is the vbox issue.